1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus each having the electrophotographic photosensitive member, and to a phthalocyanine crystal.
2. Description of the Related Art
Since a semiconductor laser commonly used in an image exposing device of an electrophotographic photosensitive member has a long oscillation wavelength in the range of 650 to 820 nm, electrophotographic photosensitive members having high sensitivity to light in the long wavelength range are currently under development.
Phthalocyanine pigments are effective as charge generating substances having high sensitivity to the light ranging to such a long wavelength region. Oxytitanium phthalocyanine and gallium phthalocyanine in particular have excellent sensitivity properties, and various crystal forms have been reported until now.
Although an electrophotographic photosensitive member using a phthalocyanine pigment has excellent sensitivity properties, a problem is that the generated photo carriers tend to remain in a photosensitive layer so as to act as a memory, easily causing potential variation such as ghosting.
Japanese Patent Application Laid-Open No. 2001-40237 discloses that the addition of a specific organic electron acceptor to a phthalocyanine pigment during acid pasting has a sensitizing effect. The method has, however, problems that the additive (organic electron acceptor) may cause chemical change and that the transformation into a desired crystal form is difficult in some cases.
Japanese Patent Application Laid-Open No. 2006-72304 discloses that wet crushing treatment of a pigment and a specific organic electron acceptor allows for simultaneous crystal transformation and incorporation of the organic electron acceptor in the surface of the crystal, resulting in improved electrophotographic properties.
Japanese Patent Application Laid-Open No. H07-331107 discloses a hydroxygallium phthalocyanine crystal which contains a polar organic solvent. With use of a transformation solvent such as N,N-dimethylformamide, a polar organic solvent is incorporated in the crystal, so that a crystal having excellent sensitivity properties is produced.
Various attempts have been made to improve electrophotographic photosensitive members as described above. For further improvement in high-quality image in recent years, it is desired to prevent image degradation due to ghosting in various environments. In the method according to Japanese Patent Application Laid-Open No. 2006-72304, the organic electron acceptors are not sufficiently contained in the produced phthalocyanine crystal, being in a simple mixture state or attached to the surface. Thus, there is a need for improvement. In the method according to Japanese Patent Application Laid-Open No. H07-331107, it was found that the generated photo carriers tend to remain in a photosensitive layer so as to act as a memory, easily causing ghosting in some cases.